01 - Heat 1 tablespoon of butter in a large saucepan over medium heat. Add the onion and cook until translucent, about 3–4 minutes. Add garlic and cook for 1 minute more.
02 - Add sliced mushrooms and sauté for 5–7 minutes, stirring occasionally, until browned and softened. Season with salt and pepper.
03 - Stir in the arborio rice and toast for 2 minutes, stirring constantly until the edges become slightly translucent.
04 - Pour in the white wine and stir until it is mostly evaporated.
05 - Add a ladleful of warm vegetable broth to the rice. Stir gently and cook until the liquid is mostly absorbed. Repeat adding broth, one ladle at a time, stirring frequently and allowing absorption before adding more, about 18–20 minutes.
06 - Taste the rice to ensure it is creamy and tender with slight bite (al dente).
07 - Remove from heat. Stir in remaining 2 tablespoons butter and grated Parmesan until creamy and well combined.
08 - Drizzle truffle oil over risotto and gently stir. Adjust salt and pepper if necessary.
09 - Serve immediately, garnished with chopped parsley and extra Parmesan if desired.